FIGS. 1A to 1C are diagrams for explaining a traditional magnetic encoder, in which a multipolar magnet and magnetic sensors such as Hall ICs as illustrated in FIG. 1A are used. In this case, Hall ICs 102a and 102b are placed such that the phase difference between each other's output pulses are offset by an electrical angle of 90 degrees. By taking such a configuration, it is possible to make a magnetic encoder able to detect a rotational direction.
FIG. 2 is a block diagram of a Hall IC in general use, in which a Hall element 101, an amp 130, and a Schmitt circuit 131 are integrated. Such a Hall IC is broadly used in fields such as magnetic pulse encoders. The Hall IC operates to amplify the Hall electromotive force output in proportion to a magnetic field applied to the magneto-sensing surface of the Hall element 101 at the amp 130, subsequently make a comparison against an arbitrary threshold at the Schmitt circuit, and digitally output the result.
Next, the principle of a magnetic encoder capable of detecting direction will be described. FIG. 1B represents the magnetic fields applied to Hall elements inside Hall ICs 102a and 102b and outputs of each Hall IC in the case where, provided that the state illustrated in FIG. 1A is an electrical angle of 0 degrees, the Hall ICs 102a and 102b are rotated therefrom about a magnet in the CCW direction. Also, FIG. 1C represents the magnetic fields applied to Hall elements inside Hall ICs 102a and 102b and outputs of each Hall IC in the case where, provided that the state illustrated in FIG. 1A is an electrical angle of 0 degrees, the Hall ICs 102a and 102b are rotated therefrom about a magnet in the CW direction. As the results demonstrate, it becomes possible to detect the rotational direction by taking the rising or the falling in the output of one of the Hall ICs as a trigger, and seeing whether the state of the output of the other Hall IC is high or low. In this example, the falling of the Hall IC 10b is set as the trigger.
However, this configuration entails the use of two separate Hall ICs, and thus it is necessary to change the placement of the Hall ICs to match the pitch of the multipolar magnet, and the effects of assembly misalignment or the like cannot be ignored. For this reason, as a technique for improving the above, there exists a technique that, as in FIGS. 1 and 2 in Patent Literature 1, enables direction detection with one chip by using magnetic convergence plates made up of a magnetic body, and utilizing a property that the phases of a vertical magnetic field and a horizontal magnetic output in conjunction with the rotation of a multipolar magnet such as in FIG. 8 of Patent Literature 1 are offset by an electrical angle of 90 degrees with respect to an electromagnetic transducer magneto-sensing surface. This method improves the problems discussed above, and is an effective technique as a magnetic encoder or input device.